From WO 2011/110637 A2 a generic filter medium of a filter element for the filtration of a fluid, in particular of a liquid fuel, water, engine oil or air is known, which comprises at least one non-woven filter layer of synthetic individual fibres. The filter medium has a degree of separation which increases in the flow direction for the particles to be filtered out. The filter layer additionally has a compressed character which increases in flow direction.
From DE 299 07 699 U1 a filter material, comprising at least one substrate material layer and at least one fibre fleece layer is known. The at least one fibre fleece layer comprises a nanofibre fleece layer with an average diameter from 10 to 1,000 nanometres and further nanofibre specific parameters. The substrate material layer in this case is constructed of a filter paper.
From DE 197 31 860 C1 in turn a filter material which is constructed of multiple layers is known, with a fibre layer which is laminated together with a paper substrate layer.